Widget overlapping Notebook

["Hylke Donker" <hylke donker gmail com>]

Hello,
I'm having some problems with an EventBox widget.
In my application, I have a Notebook widget, that contains a VBox for each
tab. After I have added an EventBox widget to my application, one of the
widgets(from a specific VBox, that is attached to the Notebook widget) is
overlapping the Notebook widget.
I have made a screenshot to show what I mean:
http://img411.imageshack.us/img411/4713/screenshot2at6.png
I've tried to use the allocate size function, but that didn't help either.
I have also asked this question on #gtk and Tristan(that was his nick on
IRC), told me on that this could possibly be a bug in the GTK+ library. (btw
tristan, I really appreciated your time and effort to help me).
I've added a stripped version of my own code(the code is written in python),
that reproduces my problem.
I hope anyone can help me.
Thanks in advance,
Hylke